In the past, promotional articles have been produced including detachable coupons, labels and the like, or having cover sheets or masks that can be removed to reveal a hidden message. For example, U.S. Pat. No. 4,307,900 shows a coupon vehicle on which indicia have been printed and covered with a layer of pressure-sensitive adhesive. A release strip is laminated over the adhesive and sectionally removed to attach a package portion, such as a proof of purchase seal, in place over the indicia.
U.S. Pat. No. 3,822,901 shows a hidden message apparatus having a sheet bearing on one side indicia covered by opaque means such as removable tape, and bearing on the other side adhesive protected by a release sheet. The main sheet is perforated to permit portions bearing the indicia to be removed and attached to some other article.
U.S. Pat. No. 4,033,611 shows a multi-ply lottery ticket folded into multiple layers permanently secured to one another and perforated to permit flaps to be lifted to reveal indicia beneath the flaps.
In another prior device, a two-ply game assembly is glued to the release sheet of a conventional bumper sticker. The game card had a play area that could be torn away from an area of the game card glued to the release sheet. The play portion consisted of an adhesive-coated layer and a release sheet having "scratch-off" areas for playing the game.
U.S. Pats. Nos. 2,321,184; 2,274,488; 3,582,111; 3,711,683; 4,004,058; and 4,059,912 show other articles having removable stickers or hidden messages or the like. U.S. Pats. Nos. 4,095,824 and 4,241,942 show secure contest cards utilizing an opaque removable mask over printed indicia.
It will be seen from an examination of these examples of the prior art that when a pressure-sensitive adhesive has been used in connection with a promotional article, a separate release sheet has been laminated against the pressure-sensitive adhesive, thus adding to the complexity and expense of the manufacturing process.